Preheat the oven to 350°F. Line a 9x13 baking dish with parchment paper, spray with non-stick cooking spray, and set aside.
Mix together melted butter, eggs, egg yolk, and strawberry cake mix in a medium mixing bowl. Use a hand mixer or stir by hand.
Spread batter into prepared baking dish. Bake for 18 minutes.
While the brownies are baking, prepare the glaze by whisking together powdered sugar, strawberry extract, and enough water to form a paste.
Remove the brownies from the oven and immediately pour glaze on top. Spread carefully to cover the top of the brownies. (You can lift the brownies from the pan by the parchment paper if you wish before spreading the glaze on.)
Allow brownies to cool completely and the glaze will set so that it’s dry to the touch. Cut into pieces and serve.
PRO TIP:The glaze and cake mix make this “fudgy” brownie sweet. Using salted butter in the recipe helps balance the sweetness a bit. You could also use canola or vegetable oil in place of the butter.PRO TIP:Bake in an 8x8-inch square baking pan for a thicker brownie - adjust cook time accordingly.PRO TIP:The brownies are done when a toothpick comes out clean or with just a few crumbles - you don’t want a wet batter, but you do want the brownies to turn out nice and chewy.PRO TIP:When mixing the glaze, add the liquid ingredients gradually to control the consistency of the glaze. Too much water/liquid will make a very runny and less opaque glaze. PRO TIP: The glaze is a thick paste, and the brownies are delicate (much like the delicate top of a baked cake) - you need the heat from the just out of the oven brownies to help melt the glaze and make it spreadable. PRO TIP:Cut the brownies after they have cooled completely and the glaze is set for a lovely crackle effect.